In the treatment of periodontitis, it is known to use hand-operated instruments, known as scalers for cleaning the tartar, concretions (the particularly hard subgingival tartar) and necrotic root element from the tooth. The dentist holds the scaler in much the same way as a writing instrument between the thumb, index finger and middle finger. The scaler is essentially a scraper provided with a handler. The scraper carries a scraping insert, with the cutting edge of which the tooth is cleaned. The middle finger is supported on the "shovel" face of the tooth and the cutting edge of the scraper insert is guided along the tooth root under the gums and from the lowest point of the gum pocket and whilst exerting pressure on the tooth root is suddenly moved with a powerful jerk in scraping manner towards the chewing face of the tooth. This process is repeated until the deposits are removed.
Each movement must be performed with a great amount of effort and very precisely, in order to avoid injury. A further problem is that the movement sequence to be performed by the dentist must be carried out with an unfavourable force application, so that the hand rapidly becomes fatigued. Therefore this constitutes one of the hardest manual activities of the dentist.